The use of damping devices, such as Helmholtz resonators, in turbine engines is known. For instance, various examples of resonators are disclosed in U.S. Pat. No. 6,530,221, which is incorporated herein by reference. Resonators can dampen undesired frequencies of dynamics that may develop in the engine during operation.
One or more resonators can be attached to a surface of a turbine engine component, such as a combustor liner. The resonators are commonly attached to the component by welding. Some resonators can include a plurality of passages through which air can enter and purge the cavity enclosed by the resonator. One beneficial byproduct of such airflow is that the component to which the resonator is attached can be impingement cooled. That is, cooling air can pass through the passages and directly impinge on the hot surface underlying the resonator housing.
The operational demands of some engines have necessitated resonators with greater damping effectiveness, which can be achieved by increasing the size of the resonators. However, one tradeoff to these larger resonators is that the cooling holes becomes less effective in cooling the surface below, especially when resonator height is increased. As the distance between the impingement cooling holes and the hot surface beneath increases, greater amounts of cooling air can disperse within the closed cavity of the resonator without impinging on the hot surface. As a result, the impingement cooling holes become less effective in cooling the hot surface. Thus, there can be concerns of overheating of the component and/or the junction between the resonator and the component (i.e. welds), which can reduce the life cycle of these components.
Increased amounts of cooling air can be directed through the resonators. However, an increase in the coolant flow through the resonator can detune the resonator so that it will no longer dampen at its target frequency range. Alternatively, additional resonators can be provided on the component; however, adding more resonators at a sub-optimal location can provide less damping effectiveness than a larger resonator at an optimal location. Further, other design constraints may sometimes limit the ability to attach more resonators at other locations.
Thus, there is a need for a system that can maintain resonator cooling effectiveness.